Staphylococci are the leading cause of bacteremia, surgical wound infections, and infection of prosthetic materials in the United States, and the second leading cause of nosocomial infections. Thus, Staphylococcal infections represent a major source of morbidity and mortality, and a large economic burden. Currently, there exists no anti-Staphylococcal vaccine in clinical use. Staphylococci express surface-exposed, cell wall lipoteichoic acid containing a highly-conserved (poly)glycerolphosphate (pgp) backbone. A monoclonal antibody specific for pgp confers passive protection against Staphylococcal infection in experimental animals, and is currently being tested in a phase III clinical trial. A method has been developed for efficient and large-scale production of synthetic pgp. A covalent conjugate of synthetic pgp and tetanus toxoid (pgp-TT) was produced that elicited boosted serum IgG anti-pgp antibodies in mice after secondary immunization. Mice immunized with pgp-TT exhibited rapid clearance of Staphylococci from the blood, in contrast to mice immunized with an irrelevant conjugate vaccine. Thus, a pgp-based conjugate vaccine represents a promising approach for active immunization against Staphylococcal pathogens, including S. aureus and S. epidermidis. Numerous factors impact on the optimal design of a conjugate vaccine. In this regard, this proposal will determine, using the mouse as a model system, the immunogenicity and protective ability of pgp that contains different chain lengths of glycerol phosphate monomers, and molar ratios of pgp to carrier protein, the effect of several different - protein conjugation chemistries, the potency of distinct protein carriers and adjuvants, the efficacy of a purely synthetic pgp-PADRE (Pan DR helper T cell epitopes) conjugate vaccine, and the relative capacity of optimized pgp conjugate vaccines to elicit protective antibodies against both S. aureus and S. epidermidis. Collectively, these studies will establish a pgp conjugate vaccine design that will be suitable for testing in humans and that has the potential to confer active, antibody-mediated protection against Staphylococcal infections. This project is a collaborative effort of a synthetic chemist for production of synthetic pgp, a biochemist for antigen conjugation, and a bacterial immunologist for testing vaccine immunogenicity and host protection. PUBLIC HEALTH RELEVANCE: Staphylococci are the leading cause of bacteremia, surgical wound infections, and infection of prosthetic materials in the United States, and the second leading cause of nosocomial infections, incurring substantial morbidity, mortality, and economic burden. Currently, there exists no anti-Staphylococcal vaccine in clinical use. In this proposal a novel conjugate vaccine will be developed, and tested in mice, for induction of protective IgG antibodies specific for the highly-conserved Staphylococcal cell wall antigen, (poly)glycerolphosphate, produced synthetically.